1. Field of the Invention
The present invention relates to a power supply circuit that generates a desired output voltage from an input voltage, and a semiconductor device for use therein.
2. Description of Related Art
FIG. 4 is a circuit block diagram showing an example of a conventional power supply circuit. As shown in FIG. 4, the conventional power supply circuit has a power supply IC 100, an inductor L101, and capacitors C101 to C103. The power supply IC 100 has field-effect transistors M101 to M106, first and second drivers DRV101 and DRV102 integrated therein, and further has terminals T101 to T108 as means for establishing external electric connection.
Inside the power supply IC 100, the transistor M101 is connected between the terminals T101 and T102. The transistor M102 is connected between the terminals T103 and T104. Gates of the transistors M101 and M102 are each connected to the first driver DRV101. Outside the power supply IC 100, the terminal T101 is connected to a ground terminal. The terminal T102 is connected to a first end of the inductor L101. A second end of the inductor L101 is connected to a terminal from which an output voltage Vout1 is outputted, and is also connected to a first end of the capacitor C101. A second end of the capacitor C101 is connected to a ground terminal. The terminal T103 is connected to a terminal to which an input voltage Vin is inputted.
That is, in the conventional power supply circuit, a step-down DC/DC converter (a switching regulator) that generates a desired output voltage Vout1 from the input voltage Vin is formed by using the transistors M101 and M102, the first driver DRV101, the inductor L101, and the capacitor C101.
Also, inside the power supply IC 100, the transistor M103 is connected between the terminals T104 and T105. The transistor M104 is connected between the terminals T105 and T106. The transistor M105 is connected between the terminals T106 and T107. The transistor M106 is connected between the terminals T107 and T108. Gates of the transistors M103 to M106 are each connected to the second driver DRV102. Outside the power supply IC 100, the terminal T104 is connected to a ground terminal. The terminal T105 is connected to a first end of the capacitor C102. The terminal T106 is connected to the terminal to which the input voltage Vin is inputted. The terminal T107 is connected to a second end of the capacitor 102. The terminal T108 is connected to a terminal from which an output voltage Vout 2 is outputted, and is also connected to a first end of the capacitor C103. A second end of the capacitor C103 is connected to a ground terminal.
That is, in the conventional power supply circuit, a double step-up charge pump that generates a desired output voltage Vout2 (=2×Vin) from the input voltage Vin is formed by using the transistors M103 to M106, the second driver DRV102, and the capacitors C102 and C103.
An example of a conventional technology related to the above description is disclosed in JP-A-2006-171367.